---
title: Glossary
description: Find definitions for the market, trading, identity, clearing, and API terms used throughout the UDX REST and WebSocket documentation.
---

UDX uses the same terms across REST, WebSocket, and FIX.

| Term | Definition |
| --- | --- |
| **Account** | A position-bearing account under one member. |
| **API Key** | A credential issued for programmatic access on behalf of a user, with explicit scopes and an optional restriction to one account. |
| **Combo** | A synonym for a multi-leg market. |
| **Contract** | The unit traded in a market. One YES contract pays $1 when the market settles YES and $0 when it settles NO. Quantities can use increments of `0.01`. |
| **DCM** | Designated Contract Market. The exchange side of UDX that lists markets, runs order books, and matches orders into trades. |
| **DCO** | Derivatives Clearing Organization. The clearing side of UDX that holds positions and balances and settles markets. |
| **Event** | A real-world proposition with a binary YES or NO outcome. |
| **Grant** | A user's authorization to act on one specific account belonging to that user's member. |
| **Idempotency Key** | An optional client-generated token on a mutating request. Resending an identical keyed request replays the original response rather than executing again. Reusing a key with a different request is rejected. |
| **L1** | Top-of-book market data: best bid and ask with aggregate size, without deeper price levels or last-trade information. |
| **L2** | Market-by-price data: the full price ladder with quantity aggregated at each level. |
| **L3** | Market-by-order data: every individual resting order and its queue position. |
| **Market** | A tradable binary contract whose settlement direction derives from one or more event outcomes. Each market has one order book. |
| **Market Catalog** | The published set of single-leg and multi-leg markets with their metadata. It is served live and never cached, because a market's trading status rides with it. |
| **Market Data** | Published order-book views at L1, L2, or L3 depth, plus trading activity such as trades and statistics. |
| **Market Lifecycle** | The trading statuses a market moves through, from `unopened` to `expired`, and the settlement that follows. |
| **Market Metadata** | A market's descriptive and trading parameters: ticker, description, status, tick size, price bounds, and expiration. |
| **Market Statistics** | A market's trading-activity summary, such as volume and open interest, as distinct from its order book. |
| **Member** | A participant that owns users and accounts. REST request capacity is shared at the member level. |
| **Multi-leg Market** | A market combining the selected outcomes of two or more component markets. Also known as a combo. |
| **Order** | An instruction to buy or sell YES contracts in one market at specified terms. Resting orders make up its order book. |
| **Order Book** | The resting buy YES and sell YES orders for a market, organized by price and queue position. |
| **Outcome** | The resolved YES or NO result of an event. |
| **Position** | An account's signed net quantity of YES contracts in a market: positive is long and negative is short. |
| **Quote** | A single-sided bid or offer answering an RFQ. |
| **Resolution** | Determining an event's YES or NO outcome from external evidence. Resolution occurs before dependent markets can settle. |
| **RFQ** | A request for quote: a solicitation for quotes in one market or a set of legs. |
| **RFQ Participant ID** | The identifier a user is known by to RFQ counterparties. |
| **Series** | A recurring family of events. |
| **Settlement** | Applying the resolved outcomes of one or more events to a market's positions and crediting the winning side. |
| **Single-leg Market** | A market whose settlement direction derives from one event outcome. |
| **Trade** | An execution created when compatible buy and sell orders match. |
| **Transfer** | An atomic movement of funds between two accounts of the same member. |
| **User** | A human or programmatic identity that authenticates and acts for a member through one or more grants. |
| **YES Contract** | The single contract traded in a market. Buying goes long YES; selling goes short YES. There is no separate NO contract. |